<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport"
        content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>
<body>
<div id="app">
<h2>test</h2>
  <p>{{foo}}</p>
</div>

<script src="../../dist/vue.js"></script>
<script>
  //断点 obsrever/index if(Dep.target)
  // 创建实例
  const app = new Vue({
    el: '#app',
    data:{
      foo:'foo'
    }
  });

</script>

</body>
</html>
